1. Field of the Invention
The present invention relates generally to a circuit interrupt system, more specifically to a circuit interrupt system for an internal combustion engine and in particular to a system for interrupting a vehicle ignition system to provide a measure of protection from theft of the vehicle.
2. Description of the Prior Art
It is often desirable to selectively interrupt or open a circuit, for example a vehicle ignition circuit to restrict use of the vehicle. Vehicle theft is a serious crime problem in this country. Most motor vehicles have keyed ignition systems which provide their owners with a certain measure of security. However, experienced car thieves are often able to circumvent the standard, factory-installed door and ignition locks.
A disadvantage with the standard, factory-installed security devices is that vehicle thieves can easily familiarize themselves with comparable security devices on other vehicles before taking illegal possession of a target vehicle. Experience has generally shown that most security systems devised and installed by vehicle manufacturers can be analyzed and circumvented by determined vehicle thieves.
After market security systems for retrofitting in existing vehicles are also available. These include alarm systems which sound an audible alarm, such as the vehicle horn or a siren, when the vehicle is tampered with by an unauthorized person. Other security systems require the input of a predetermined code, such as a series of numbers or letters, before the engine can be started.
Mechanical security devices are also available which physically restrain certain vehicle controls, such as the steering wheel or shift lever. Although a certain measure of security is probably provided by all of these devices, they tend to suffer from significant disadvantages relating to relatively high costs of manufacture and installation, accidental actuation which can drain the vehicle's battery, inconvenient activation and deactivation, and ineffectiveness against skilled thieves.
The losses from vehicle theft are passed on to vehicle owners in general in the form of higher insurance rates and public spending for law enforcement. Vehicle theft is a major crime problem whose active participants range from teenagers who only "borrow" vehicles for "joy rides" to organized criminal enterprises which dismantle large volumes of stolen vehicles. Owners of certain types of late model vehicles, which are highly sought by professional thieves and thus considered "targets", may particularly be penalized by widespread auto theft through higher insurance premiums.
The vehicle theft crime problem is not limited to automobiles. Trucks, construction equipment, farm equipment, boats and aircraft are all susceptible to theft losses. Many of these vehicles can be quickly transported under their own power once their engines are started. On the other hand, relatively few vehicles are stolen without starting their engines. Thus, a relatively effective way to deter vehicle theft is to prevent the unauthorized operation of vehicle engines. The circuit interrupt system of the present invention effectively addresses the aforementioned problems associated with existing vehicle security systems.